Re: Robert Warner
Without more information it would be difficult to find your grandfather. Do you know if your grandfather Robert had any brothers or sisters? Did he have a middle name (even an initial would help)? Do you know where your grandparents got their divorce? The divorce papers may be helpful. Do you know if your grandfather remarried and had any more children? Your father's marriage record may have some helpful data on your grandfather (your father may have known where he was living at the time). If you're no sure ask any living relatives if they know anything. Family stories can often be helpful (oh yeah, he had a sister Mabel who married Frank Jones; they lived in...).
The Great Chicago Fire was in 1872 so it would has no bearing on your search.